The imaging features and prognosis of primary central airway salivary gland-type tumor

Abstract

Objective To analyze the image features and prognosis of primary central airway salivary gland-type tumor (SGT). Methods The clinical and imaging data of 25 cases with SGT confirmed by histopathology were retrospectively analyzed in our hospital from October 2009 to November 2017. Follow up of patients for survival was performed. Among 25 cases of SGT, there were 14 cases of adenoid cystic carcinoma (ACC), ten cases of mucoepidermoid carcinoma (MEC) and one case of mucoepidermoid carcinoma (EMC). All cases had non-enhanced CT scans (among which 20 cases underwent CT scan with contrast). Post-processing were performed to evaluate the location, range, density, degree of enhancement of the lesions and involvement of hilar or mediastinal lymph nodes. Eight cases underwent PET/CT imaging and one underwent MR imaging, respectively. Independent sample t test was used to compare difference in ages between ACC group and MEC group. Nonparametric test was performed to compare difference in tumor′s diameter between ACC group and MEC group. Comparison of genders, history of smoking, tumor-node-metastasis (TNM) stage and CT features between ACC group and MEC group were tested using Fisher′s exact tests. Survival was calculated using the Kaplan-Meier method, and the survival curves were compared by the log-rank test. Results Compared to MEC, patients with ACC were older. There were significant difference between the two groups (t=3.154, P<0.05). ACC tended to involved trachea or main bronchi (13/14) while MEC were mostly located at lobar or segment bronchi (6/10). The shape of ACC tumors were mainly lobulated or presented as circumferential wall thickening (13/14), while MECs were smoothly oval (7/10). On contrast-enhanced CT scans, ACC mainly showed mild or moderate enhancement (9/10), While most of MEC had shown avid enhancement (8/10). CT findings suggestive of airway obstructive disease were seen more with MEC (9/10) than ACC (4/14). There were significant differences of the above CT features between ACC and MEC group (P<0.05). A case of EMC in an 43 years old female presented rounded nodule in tracheal; The SUVmax in 6 of 8 cases of PET/CT exceeded 2.2; Overall survival (OS) was 87.5% in all cases. No significant difference was found between ACC and MEC groups regarding OS (χ2=0, P=1.000). Ages, surgical and nonsurgical patients and TNM stage were found to be related to OS (χ2=13.799, 13.799, 13.171, respectively, P<0.05). Conclusions Primary central airway salivary gland-type tumors are commonly occurred in patients at a low age, with weak invasive feature and good prognosis. The predominant site and CT characteristics between ACC and MEC were significantly different. Key words: Salivary gland neoplasms; Tomography, X-ray computed; Magnetic resonance imaging; Prognosis